Mobile communication devices and their environments are becoming increasingly complicated and the security demands of communication are increasing respectively.
The increase of the number of devices and services providing information or distributed content through wireless communications has created new demands for security of communications.
Moreover, the users of mobile information services are increasingly interested not only on security, but also on their privacy. The users do not generally want to adopt new services if there is doubt on the protection of the users' data. There are also differing needs depending on the service and information. Thus, it has become increasingly difficult to manage how each piece of information should be stored and shared with other devices or users.